Pulp preparing apparatus



K. A. SKARDAL ET AL PULP PREPARING APPARATUS V May 3, 1955 2 Shets-Sheet1 Filed Feb. 25, 1955' M 195.5 K. A. SKARDAL EI'AL 2,707,420

PULP PREPARING APPARATUS Filed Feb. 25, 1953 2 Sheets-Sheet 2 UnitedStates Patent PULP PREPARING APPARATUS Karl Arvid Skardal, Stockholm,and Olov Birger Biirjeson, Bromma, near Stockholm, Sweden, assignors toLeje & Thurne Aktiebolag, Stockholm, Sweden Application February 25,1953, Serial No. 338,756 Claims priority, application Sweden December11, 1952 2 Claims. (Cl. 92--26) The present invention relates to anapparatus for preparing a pulp suitable for supplying it directly orsubsequently to some preparatory treatment to a paper making machine.

More particularly, the invention relates to that type of such apparatuswhich comprises a tank for receiving a liquid and the stock from whichthe pulp is to be formed, said tank having at its bottom a rotorprovided with impeller blades for beating and circulating the contentsof the/tank and, eventually, also for discharging the prepared pulp asit reaches a predetermined consistency.

The object of the invention is to provide an apparatus of this type,which may yield a high degree of efliciency and may positively removesuch solid elements which are not suitable as ingredients of theprepared pulp.

According to a feature of the invention guiding elements are providedinside the tank for leading the contents of the tank held in acirculation by the rotor in an ascending path in order thereby to obtaina positively controlled and intensified circulation, said guidingelements being so constructed and arranged as not to prevent the returnflow of the circulating tank contents downwardly towards the center ofthe rotor.

Another feature of the invention resides in the provision inside thetank of guiding elements forming a path ascending like a spiral alongthe rounded, preferably cylindrical circumferential wall of the tank.

A still another feature of the invention resides in the provision at thetop of the said guiding path of a, preferably removable, grid structure,like a comb or the like, for catching such coarse or big objects in thetank contents, which remain practically unaffected in the contents asthe rest thereof has attained the desired state of fineness. It is to benoted, however, that such a removal of coarse objects may be madewhenever desired during the operation of the apparatus.

In the accompanying drawings one form of the invention is illustrated.

Figure 1 is a side elevation of the apparatus and Fig. 2 is a top planview thereof.

Figs. 3-8 are detail sections taken on the lines 3-3, 4-4, 5-5, 66, 77and 8-8, respectively, of Fig. 2.

It is understood that the construction shown and hereinafter describedis an example only, and that variations may be made within the scope ofthe invention as claimed.

In the example shown the numeral 1 indicates the circumferential wall ofa cylindrical tank having a funnelshaped bottom 3 tapering towards aneccentrically positioned circular opening 2. In said opening a rotor isdis posed, though it may, if desired, be disposed above the opening. Therotor may comprise a circular disc 4 supported by a depending verticalshaft 20. Provided on the upper surface of disc 4 is a set of impellerblades 5. Similar blades may be provided also in the lower surface ofthe disc in order to allow the rotor to be used also as a pump wheel. Tothis end there may be provided a pump housing 6 having an outletindicated at 2,707,420 Patented May 3, 1955 6 in Fig. 1. As far as theinvention claimed is con cerned the construction of the rotor may bevaried, provided it may produce a beating and circulating action on thecontents of the tank.

In the example shown the diameter of the opening 2 is considerablygreater than that of the disc 4 for the purpose of mounting the rotor inthe casing 6'. The annular space thus resulting between thecircumference of the disc 4 and that of the opening 2 is covered by anannular plate 7 except for a narrow circular gap 8 immediatelysurrounding the disc 4, as indicated in Fig. 2.

The rotor due to the eccentrical location of the opening 2 is situatednot far from the circumferential wall of the tank. The portion of therotor next to said wall is covered by a heliciform casing which is openinwardly and towards the rotor center and forwardly in the direction ofrotation of the rotor. Said heliciform casing may comprise, forinstance, an upper Wall 9 ascending in an oblique direction from thebottom of the tank and a curved side wall It extending from a point 11of the bottom of the tank near the opening 2 of a point 12 at a higherlevel of the funnel-shaped bottom, see especially Fig. 6. Extending fromanother point 13 adjacent the opening 2 which is located in front of theforwardly directed outlet end of the heliciform casing 9, 10 at acertain distance therefrom, as shown in Fig. 2, is a guide wall 14forming a helical ascent along the circumferential wall 1 of the tank.The peripheral extension of said guide wall is about half thecircumference of the tank.

Rotatably mounted in a bearing 19 at the upper edge of the tank wall 1is a shaft 15 which extends inwards in a substantially horizontal andradial direction and carries a set of pins 16 which form a grid or comblike structure in front of the discharge end of the guide wall 14. Thepins are preferably curved towards the discharge end of the guide wall,as shown in Fig. 3, to allow them easily to catch coarse or big solidobjects sliding up along the guide wall. Externally of the tank theshaft 15 is provided with a control mechanism including a handle 17, bymeans of which the grid or comb structure 16 may be swung upwards fordischarging the material caught thereby. Said control mechanism alsoincludes means, as indicated at 18 in Fig. 2, for locking the shaft 15with the pins 16 in their depending or raised position.

The operation is as follows: The impeller blades 5 of the rotor 4 beatsand circulates the contents of the tank, which consists of a liquid, aswater, and various kinds of paper-making material, as pieces of ordinarypaper pulp or waste paper. The heliciform casing 9, 10 catches thecirculating contents as it is beaten by the impeller blades and set inmotion thereby, and leads it onto the guide wall 14, whereby thecontents of the tank receives an, at least partially, positivelycontrolled circulation, while still quite free to flow downwards fromthe top of the tank towards the center of the impeller wheel to be thenagain beaten and thrown out to be caught by the heliciform casing. Thepaper-making material of the circulating contents of the tank will, as aresult, he more effectively broken up than would be the result of aquite free circulation.

The charging of the tank may be either intermittent or continuous. Whencontinuous charging is used the catching grid or comb 16 is lowered to aposition in front of the discharge end of the guide wall 14, either asthe pulp prepared has attained a predetermined state of fineness orotherwise, whenever it may be desired to catch and remove solid objectsnot sufliciently broken up. The removal of the objects caught iseffected by swinging the grid or comb 16 upwards and outwards over theedge of the tank. In case of continuous charging the operation of thegrid or comb 16 may take place at suitable intervals.

Attention is again invited to the fact that variations may be madewithout departing from the scope of the annexed claims.

We claim:

1. An apparatus for preparing a pulp for paper manufacturing, comprisinga tank including a substantially cylindrical side wall and a bottom wallfor receiving a liquid and material to be mixed with the liquid forpreparing a paper stock, an impeller eccentrically mounted at the bottomof said tank adjacent the side Wall thereof for beating and circulatingthe stock, a heliciform housing surrounding the portion of said impellersituated next to the side wall of the tank for re ceiving and guiding aportion of the stock discharged from the impeller, a spiral rampextending along a portion of the side wall. of the tank from a point atthe bottom of the tank in front of the delivery end of said heliciformhousing to a point not far from the top of the tank for receiving thematerial delivered from said housing and allowing it to rise along theupper surface of the ramp to about the level of the stock in the tank,and means in front of the upper end of the ramp for catching coarseobjects carried with the material that leaves the ramp at the upper endthereof.

2. An apparatus for preparing a pulp for paper manufacturing comprisinga tank including a cylindrical side wall and a bottom tapering towardsan eccentrically positioned circular opening, an impeller wheelrotatably mounted in said opening, a heliciform housing provided betweenthe portion of said impeller which is situated next to the side wall ofthe tank, said heliciform housing having a side wall forming a smoothtransition to the side Wall of the tank, a spiral ramp provided along aportion of the side wall of the tank for constituting a path graduallyrising from the bottom of the tank in front of the delivery end of saidheliciform housing up to a level not far from the top of the tank, andmeans rotatively mounted in the side Wall of the tank in front of theupper end of the ramp for catching coarse objects p, carried along theupper surface of the ramp. by the stock passing upwardly along saidsurface.

References Cited in the file of this patent UNITED STATES PATENTS

1. AN APPARATUS FOR PREPARING A PULP FOR PAPER MANUFACTURING, COMPRISINGA TANK INCLUDING A SUBSTANTIALLY CYLINDRICAL SIDE WALL AND A BOTTOM WALLFOR RECEIVING A LIQUID AND MATERIAL TO BE MIXED WITH THE LIQUID FORPREPARING A PAPER STOCK, AN IMPELLER ACCENTRICALLY MOUNTED AT THE BOTTOMOF SAID TANK ADJACENT THE SIDE WALL THEREOF FOR BEATING AND CIRCULATINGTHE STOCK, A HELICIFORM HOUSING SURROUNDING THE PORTION OF SAID IMPELLERSITUATED NEXT TO THE SIDE WALL OF THE TANK FOR RECEIVING AND GUIDING APORTION OF THE STOCK DISCHARGED FROM THE IMPELLER, A SPIRAL RAMPEXTENDING ALONG A PORTION OF THE SIDE WALL OF THE TANK FROM A POINT ATTHE BOTTOM OF THE TANK IN FRONT OF THE DELIVERY END OF SAID HELICIFORMHOUSING TO A POINT NOT FAR FROM THE TOP OF THE TANK FOR RECEIVING THEMATERIAL DELIVERED FROM SAID HOUSING AND ALLOWING IT TO RISE ALONG THEUPPER SURFACE OF THE RAMP TO ABOUT THE LEVEL OF THE STOCK IN THE TANK,AND MEANS IN FRONT OF THE UPPER END OF THE RAMP FOR CATCHING COARSEOBJECTS CARRIED WITH THE MATERIAL THAT LEAVES THE RAMP AT THE UPPER ENDTHEREOF.